ALDH1A2 moved from the lower epidermis (basal layer) to the upper epidermis (granulosum layer) following acute UVB in SKH-1 mice [158,159]; but mRNA levels in whole tissue homogenates were not altered by chronic UVB or in cSCC tumors from Ptch1+/−/SKH-1 mice [160]. This evidence concerns the gene PTCH1 and skin squamous cell carcinoma.